find-composite-type-dependencies-refactor.patch

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 6a17399..83f8be0 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -3378,23 +3378,6 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode)
 	}
 
 	/*
-	 * If we change column data types or add/remove OIDs, the operation has to
-	 * be propagated to tables that use this table's rowtype as a column type.
-	 * newrel will also be non-NULL in the case where we're adding a column
-	 * with a default.  We choose to forbid that case as well, since composite
-	 * types might eventually support defaults.
-	 *
-	 * (Eventually we'll probably need to check for composite type
-	 * dependencies even when we're just scanning the table without a rewrite,
-	 * but at the moment a composite type does not enforce any constraints,
-	 * so it's not necessary/appropriate to enforce them just during ALTER.)
-	 */
-	if (newrel)
-		find_composite_type_dependencies(oldrel->rd_rel->reltype,
-										 oldrel->rd_rel->relkind,
-										 RelationGetRelationName(oldrel));
-
-	/*
 	 * Generate the constraint and default execution states
 	 */
 
@@ -4055,7 +4038,7 @@ ATExecAddColumn(AlteredTableInfo *tab, Relation rel,
 	Oid			typeOid;
 	int32		typmod;
 	Form_pg_type tform;
-	Expr	   *defval;
+	Expr	   *defval = NULL;
 
 	attrdesc = heap_open(AttributeRelationId, RowExclusiveLock);
 
@@ -4304,6 +4287,20 @@ ATExecAddColumn(AlteredTableInfo *tab, Relation rel,
 		tab->new_changeoids = true;
 
 	/*
+	 * If we're adding an OID column, the operation has to be propagated to
+	 * tables that use this table's rowtype as a column type.  But we don't
+	 * currently have the infrastructure for that, so just throw an error.
+	 * We also forbid the case where we're adding a column with a default, since
+	 * composite types might eventually support defaults, and ALTER TABLE ..
+	 * ADD COLUMN .. DEFAULT would be expected to initialize the newly added
+	 * column to the default in each instantiation of the rowtype.
+	 */
+	if (isOid || defval)
+		find_composite_type_dependencies(rel->rd_rel->reltype,
+										 rel->rd_rel->relkind,
+										 RelationGetRelationName(rel));
+
+	/*
 	 * Add needed dependency entries for the new column.
 	 */
 	add_column_datatype_dependency(myrelid, newattnum, attribute.atttypid);
@@ -4975,6 +4972,16 @@ ATExecDropColumn(List **wqueue, Relation rel, const char *colName,
 
 		/* Tell Phase 3 to physically remove the OID column */
 		tab->new_changeoids = true;
+
+		/*
+		 * The OID removal operation needs to be propagated to tables that use
+		 * this table's rowtype as a column type.  But we don't currently have
+		 * the infrastructure for that, so just throw an error if it would be
+		 * required.
+		 */
+		find_composite_type_dependencies(rel->rd_rel->reltype,
+										 rel->rd_rel->relkind,
+										 RelationGetRelationName(rel));
 	}
 }
 
@@ -6442,17 +6449,15 @@ ATPrepAlterColumnType(List **wqueue,
 					 errmsg("ALTER TYPE USING is not supported on foreign tables")));
 	}
 
-	if (tab->relkind == RELKIND_COMPOSITE_TYPE
-		|| tab->relkind == RELKIND_FOREIGN_TABLE)
-	{
-		/*
-		 * For composite types, do this check now.  Tables will check
-		 * it later when the table is being rewritten.
-		 */
-		find_composite_type_dependencies(rel->rd_rel->reltype,
-										 rel->rd_rel->relkind,
-										 RelationGetRelationName(rel));
-	}
+	/*
+	 * If we change column data types, the operation has to be propagated to
+	 * tables that use this table's rowtype as a column type.  But we don't
+	 * currently have the infrastructure for that, so just throw an error
+	 * if it would be required.
+	 */
+	find_composite_type_dependencies(rel->rd_rel->reltype,
+									 rel->rd_rel->relkind,
+									 RelationGetRelationName(rel));
 
 	ReleaseSysCache(tuple);